Piezoelectric ceramics are used for a variety of electronic components, such as a piezoelectric actuator, which utilize, as a mechanical driving source, displacement or force generated via a piezoelectric phenomenon. With broadened use of piezoelectric actuators, multi-layer piezoelectric actuators from which larger displacement or larger generated force can be obtained at lower voltages have become increasingly used. Generally, piezoelectric actuators are desired in their functional aspect to have large piezoelectric strain constants, especially a large d33 constant and a large d31 constant as much as possible, and it is also important that they do not degrade in insulation properties during their continuous driving.
As a piezoelectric ceramic composition suitable for such purposes, there is known a composition the formula of which expressed in molar ratio is Pb1-x-ySrxBay(Zn1/3Sb2/3)aZrbTi1-a-bO3, wherein x, y, a and b satisfy 0≤x≤0.14, 0≤y≤0.14, 0.04≤x+y, 0.01≤a≤0.12 and 0.43≤b≤0.58 (see, for example, Patent Document 1), and it is described that such a piezoelectric ceramic composition is fired at 1240 to 1300° C.
Moreover, as piezoelectric ceramic compositions capable of being fired at low temperature, there are known a piezoelectric ceramic composition containing PbZrO3—PbTiO3—Pb(Zn1/3Sb2/3)O3 as a main component, containing elements Bi and Fe in an amount of 5 to 15% by mass in terms of BiFeO3, and having been fired at 1000 to 1100° C., and a piezoelectric ceramic composition containing Li, Bi and at least one of Cd, B, Pb, Si and Zn in addition to the above-mentioned main component and having been fired at 900 to 1000° C. (see, for example, Patent Document 2).
Patent Document 3 discloses a multi-layer electronic component including a piezoelectric ceramic made of crystal grains of a lead zirconate titanate-type crystal containing at least one of Sb and Nb, Zn, and Bi, and an internal electrode layer containing Ag as a main component, and a manufacturing method therefor including adding a Bi2O3 powder to a calcined powder containing at least one of Sb and Nb, Pb, Zr, Ti, and Zn, followed by firing at 920 to 960° C.